Apparatus for heating copy paper for electrostatic copiers

ABSTRACT

In using the method of contact transfer of electrostatic images developed by a tacky toner shown in our co-pending application, Ser. No. 155,108, filed June 21, 1971, it is advantageous to heat the plain paper to which the developed images are to be transferred. An improved heating assembly is provided which will ensure that the paper will not burn or char. A passageway is formed between a radiant heating assembly and a manifold which connects with an exhaust blower. The paper is drawn from the storage roller through this passageway around a tensioning roller which may be independently heated and then brought into contact with the photoconductive surface bearing the tacky toner developed image.

United States Patent [1 1 Smith et al.

[4 1 Sept. 4, 1973 1 APPARATUS FOR HEATING COPY PAPER FOR ELECTROSTATICCOPIERS [75] Inventors: Ian Edward Smith, Lockleys; Peter John Hastwell,Elizabeth Grove; Ma -inns Cornelus yermeulen, Valley View, all of SouthAustralia [73] Assignee: Savin Business Machines Corporation, Valhalla,NY.

[22] Filed: Dec. 27, 1971 [21] Appl. No.: 212,081

[52] US. Cl. 219/216, 219/388, 263/6 E [51] Int. Cl. H05b 1/00 [58]Field of Search 219/216, 388; 34/48;

355/9; 263/6 E; 338/316; 250/65 T, 65 ZE; 118/620; 117/17.5

[56] References Cited UNITED STATES PATENTS 3,053,962 9/1962 Cerasani eta1. 219/388 3,359,404 12/1967 Limberger 219/216 Meienhofer 34/48 Garbe219/388 X Primary ExaminerC. L. Albritton Attorney-Henry L. Shenier,Francis M. OConnor et a1.

[57] ABSTRACT In using the method of contact transfer of electrostaticimages developed by a tacky toner shown in our copending application,Ser. No. 155,108, filed June 21, 1971, it is advantageous to heat theplain paper to which the developed images are to be transferred.

An improved heating assembly is provided which will ensure that thepaper will not burn or char. A passageway is formed between a radiantheating assembly and a manifold which connects with an exhaust blower.The paper is drawn from the storage roller through this passagewayaround a tensioning roller which may be independently heated and thenbrought into contact with the photoconductive surface bearing the tackytoner developed image.

13 Claims, 4 Drawing Figures APPARATUS FOR HEATING COPY PAPER FORELECTROSTATIC COPIERS BACKGROUND OF THE INVENTION Our co-pendingapplication, Ser. No. 155,108, filed June 21, 197l, discloses a novelmethod for contact transfer of a liquid suspended tacky toner. We havefound that it is advantageous to heat the paper to facilitate thetransfer of the tacky toner developed image to the paper. Heating of thepaper dehumidifies it so that the moisture present on the paper on humiddays will not interfere with the transfer process. The resinous materialin the tacky toner may be thermoplastic. In such case, heating the paperincreases the fluidity of the toner resin and enables it to flow morereadily into the interstices of the plain paper to which it is beingtransferred. In every case, image transfer to the paper is facilitated.The elevated temperature aids in the evaportion of the light diluent inwhich the tacky toner is disseminated. The use of a hot air hood in thevicinity of the transfer area operates as long as there is paperpresent. If, however, there is no paper between the hot air stream andthe photoconductive surface, there is danger that there will be anelevation of temperature to an extent which will be deleterious to thephotoconductive properties of the photoconductor. Many photoconductivematerials will lose some of their photoconductive properties attemperatures about 70C.

The use of radiant heat from an infrared lamp, or an infrared sourcesuch as a resistance wire heated to redness, can be used to heat paper.This is satisfactory as long as the paper is moving. We have found that,if the paper dwells too long exposed to a high temperature infraredsource, it may scorch or even ignite.

It is also possible to heat a roller around which the paper passes. Wefound that, if we relied solely on such as the sole source of heat, thetemperature had to be so high that heat was applied too quickly, withthe result that internal stresses wrinkled the paper.

Our invention solves the problem of providing a simple and efficientmethod of heating the paper to a desirable temperature while maintainingthe paper in a smooth flat condition and ensuring that the paper willnot char or ignite even though it be stopped in the heating zone forlong periods of time.

SUMMARY OF THE INVENTION One object of our invention is to provide anovel assembly for preheating copy paper before contacting it with atacky toner liquid developed image.

Another object of our invention is to provide an improved heatingapparatus adapted to remove excess moisture from the copy paper used inelectrophotographic apparatus.

A further object of our invention is to provide an improved paper heaterwhich will not scorch or ignite the paper.

A still further object of our invention is to provide a heating assemblyfor paper adapted to contact a tacky toner developed image in which thepaper will not wrinkle or distort during the heating step.

Other and further objects of our invention will appear from thefollowing description:

In general, our invention contemplates the provision of a paper passagethrough which paper is drawn from a storage roll on its way to beingcontacted with the photoconductive drum on which the developed image islodged. The paper passage is provided with a radiant heater on one sideand a perforated plate on the other. The perforated plate communicateswith a chamber with which the suction side of an exhaust blower isconnected. The chamber provides an area of reduced pressure which servesto hold the paper against the perforated plate and ensures that itremains out of contact with the radiant heater. The suction blower alsoremoves any vapors which might be evaporated from the paper by theradiant heat. If desired, we provide auxiliary heating means adapted toheat a tensioning roller to a lower temperature than the radiant heatexisting in the paper passage. The arrangement is such that, though thepaper reside in the passage for long periods of time, it will not scorchor ignite.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings, whichform part of the instant specification and which are to be read inconjunction therewith, and in which like reference numerals are used toindicate like parts in the various views:

FIG. 1 is a sectional elevation of a paper heating assembly showing aportion of the photoconductive surface and the path of the paper fromthe roll to the photoconductive surface.

FIG. 2 is a rear elevation, with parts broken away, of the heatingassembly shown in FIG. I viewed along the line 2-2 of FIG. 1.

FIG. 3 is a fragmentary sectional view showing the tensioning rollerheater viewed along the line 33 of FIG. 1.

FIG. 4 is a sectional view taken along the line 4-4 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT More particularly, referring nowto the drawings, a roll of copy paper 2, which is plain paper, ismounted for rotation on a shaft 4 above the heating assembly which isindicated generally by the reference numeral 10. A funnel guide 6 isadapted to direct paper to a pair of paper guide rollers 8 for passagethrough the paper passage 12. A plate 14 is provided with a pair offlanges 16 adapted to secure the assembly by screws 18 to the frame ofthe electrophotographic machine (not shown). The plate 14 is providedwith openings 20 communicating with the atmosphere. A centrifugalexhaust fan 20a is provided with a duct 22 to take suction from achamber 24. This chamber is formed by a plate 26 spaced from the plate14 by end flanges 28. The plate 26 is provided with openings 30 so thatthe reduced pressure within the chamber 24 may act on the paper 3 whichlies against the plate 26. Spaced from the surface of plate 26, we mounta copper or brass plate 32, which is secured to a layer ofheat-insulating material such as asbestos board 34.

Referring now to FIGS. 2 and 4, we mount a mica sheet 36 within a recessformed in the asbestos board 34 by means of bolts 38 and ceramicferrules 40. The mica sheet 36 carries a nichrome electrical resistancewinding 42 adapted to be connected to any appropriate electricalpotential source (not shown). As will be seen by reference to FIG. 4,the mica sheet 36 and its electrical resistance winding is positioned inthe recess or pocket formed in the heat-insulating layer 34. The copperor brass plate 32 extends adjacent to but spaced from the radiant heatassembly just described, as can be seen by reference to FIG. 4. In orderto prevent the heat-conductive plate 32 from warping, we mount aplurality of rods 44 across the plate, as can be seen by reference toFIGS. 1 and 2. The resistance of the resistance winding, the voltageapplied, and the relationship of the parts are such that the plate 32will be maintained at a temperature between 350F and 450F. The paper ispositioned about one-half inch from the radiating plate 32. The lowertemperature of 350F can be maintained with about 700 watts of energy.For highspeed operation, we prefer to raise the temperature of theheat-conductive plate 32 to about 450F. This will require about 1200watts. We have maintained a sheet of paper in the paper passage with theheat-conductive plate 32 at a temperature of 450F for over an hourwithout charring the paper or having it ignite. It will be understood,of course, that in days of high humidity it is desirable to raise thetemperature of the heatradiating wall. This is done by means of apotentiometer (not shown) between the voltage source and the resistancewinding 42. The length of the paper passage, as shown in FIG. 1, istwelve inches.

The blower a is operated at a speed to move about sixteen cubic feet ofair per minute. The perforations 20 break the suction within the chamber24 to such an extent that the paper, while being held against the plate26, will not be so held with such force as to create excessive friction.Water vapor expelled from the paper by the radiant heat from the heatingplate 32 is removed by the centrifugal blower.

As soon as the paper leaves the paper passage, owing to its low specificheat, it will cool rapidly. The paper must be kept tensioned and, forthis purpose, we provide a tensioning roller 46 mounted on a shaft 48between a pair of arms 50 pivoted about pins 52. Each of the arms 50 isbiased by a spring 53. The roller 46 is two inches in diameter and itslength is about eleven and one-half inches for a paper sheet eight andone-half inches in width. If the tensioning roller 46 were unheated, itwould accelerate the cooling of the paper which must still pass aroundthe rubber pressure roller 54 mounted on-a shaft 60a for line contactwith the surface of the photoconductive drum 56 upon which the imagewhich has been developed by the tacky toner is lodged. To prevent thepaper from becoming too cool, we may mount an infrared strip heater 58provided with a resistance winding 60 adapted to be connected to asuitable potential source (not shown). The arrangement is such that theroller 46 will be maintained at a temperature in the vicinity of 250F. Apotentiometer (not shown) is adapted to control the heat to which thestrip heater 58 is heated. On humid days and at higher speeds ofoperations, a greater wattage will be required by the strip heater.

We have not shown the passage of the paper after it leaves the rubberroller 54 since this is shown in our copending application aboveidentified.

It will be seen that we have accomplished the objects of our invention.We have provided a novel assembly for preheating copy paper beforecontacting it with a tacky toner developed image. Our heating assemblyis adapted to remove excess moisture from the copy paper which mightinterfere with rapid and complete transfer of the tacky toner developedimage from the photoconductive surface to the paper. The arrangement issuch that our heater will not scorch the paper or ignite it. Thetensioning roller, acting with the paper guide rollers, keeps the papertaut so it will not contact the radiating surface in the paper-heatingpassage. In addition, we provide a chamber maintained as a zone ofreduced pressure to prevent the paper from touching the heat-radiatingsurface. The suction fan, which we ates the reduced pressure in thesuction chamber, also carries away moisture liberated from the paper bythe radiant heat.

It will be understood that certain features and subcombinations are ofutility and may be employed without reference to other features andsubcombinations. This is contemplated by and is within the scope of ourclaims. It is further obvious that various changes may be made indetails within the scope of our claims without departing from the spiritof our invention. It is, therefore, to be understood that our inventionis not to be limited to the specific details shown and described.

Having thus described our invention, what we claim 1. A copy paperheater for heating paper adapted to be moved along a path from a papersupply to a photoconductive member including in combination, a firstimperforate plate of thermally conductive material, an electricalresistance winding, means including thermal insulating means mountingsaid thermally conductive plate with one side thereof in relativelyclosely spaced relationship to said resistance winding to cause saidplate to be heated upon energization of said resistance winding, asecond plate, means mounting said second plate in relatively closelyspaced relationship to the other side of said first plate to form anelongated paper passageway in said path, said insulating materialextending over said winding, and means positioning paper from saidsupply in said passageway adjacent to the second plate and remote fromthe first plate.

2. A copy paper heater as in claim. I in which said positioning meanscomprises a pair of paper guide rollers I adjacent one end of saidpassageway a tensioning roller adjacent the other end of saidpassageway, means mounting said tensioning roller for movement towardand away from said path and means for biasing said tensioning rollerinto engagement with paper moving along said path.

3. A copy paper heater as in claim 1 in which said positioning meansincludes a tension roller, means mounting said tensioning roller formovement toward and away from said path, means biasing said tensioningroller for movement into said path and means for heating said tensioningroller.

4. A copy paper heater as in claim 1 in which said second plate isperforated, said heater including a third plate spaced from said secondplate and defining a chamber therewith, and means providingcommunication between said chamber and a zone of reduced pressure, andin which said positioning means comprises a pair of paper guide rollersadjacent one end of said passageway, a tensioning roller adjacent theother end of said passageway, means mounting said tensioning roller formovement toward and away from said path and means for biasing saidtensioning roller into said path.

5. A copy paper heater as in claim 2 in which said second plate isformed with openings, and means for providing communication between saidopenings and a zone of reduced atmospheric pressure.

6. A copy paper heater as in claim 5 in which said zone of reducedatmospheric pressure comprises the intake of a centrifugal blower.

7. A copy paper heater as in claim 2 in which said first plate is freeat one end to provide room for expansion during heating of the same.

8. A copy paper heater as in claim 7 including a plurality of meansextending across said passageway for restraining warping of said firstplate.

9. A copy paper heater as in claim 2 in which said second plate isformed with openings, a third plate spaced from said second plate anddefining a chamber therewith, and means providing communication betweensaid chamber and a zone of reduced pressure.

10. A copy paper heater as in claim 9 in which said third plate isforaminous.

11. A copy paper heater as in claim 9 in which said zone of reducedpressure comprises the intake of a centrifugal blower.

12. A copy paper heater as in claim 1 in which said radiant heater isadapted to heat said first plate to a

1. A copy paper heater for heating paper adapted to be moved along apath from a paper supply to a photoconductive member including incombination, a first imperforate plate of thermally conductive material,an electrical resistance winding, means including thermal insulatingmeans mounting said thermally conductive plate with one side thereof inrelatively closely spaced relationship to said resistance winding tocause said plate to be heated upon energization of said resistancewinding, a second plate, means mounting said second plate in relativelyclosely spaced relationship to the other side of said first plate toform an elongated paper passageway in said path, said insulatingmaterial extending over said winding, and means positioning paper fromsaid supply in said passageway adjacent to the second plate and remotefrom the first plate.
 2. A copy paper heater as in claim 1 in which saidpositioning means comprises a pair of paper guide rollers adjacent oneend of said passageway a tensioning roller adjacent the other end ofsaid passageway, means mounting said tensioning roller for movementtoward and away from said path and means for biasing said tensioningroller into engagement with paper moving along said path.
 3. A copypaper heater as in claim 1 in which said positioning means includes atension roller, means mounting said tensioning roller for movementtoward and away from said path, means biasing said tensioning roller formovement into said path and means for heating said tensioning roller. 4.A copy paper heater as in claim 1 in which said second plate isperforated, said heater including a third plate spaced from said secondplate and defining a chamber therewith, and means providingcommunication between said chamber and a zone of reduced pressure, andin which said positioning means comprises a pair of paper guide rollersadjacent one end of said passageway, a tensioning roller adjacent theother end of said passageway, means mounting said tensioning roller formovement toward and away from said path and means for biasing saidtensioning roller into said path.
 5. A copy paper heater as in claim 2in which said second plate is formed with openings, and means forproviding communication between said openings and a zone of reducedatmospheric pressure.
 6. A copy paper heater as in claim 5 in which saidzone of reduced atmospheric pressure comprises the intake of acentrifugal blower.
 7. A copy paper heater as in claim 2 in which saidfirst plate is free at one end to provide room for expansion duringheating of the same.
 8. A copy paper heater as in claim 7 including aplurality of means extending across said passageway for restrainingwarping of said first plate.
 9. A copy paper heater as in claim 2 inwhich said second plate is formed with openings, a third plate spacedfrom said second plate and defining a chamber therewith, and meansproviding communication between said chamber and a zone of reducedpressure.
 10. A copy paper heater as in claim 9 in which said thirdplate is foraminous.
 11. A copy paper heater as in claim 9 in which saidzone of reduced pressure comprises the intake of a centrifugal blower.12. A copy paper heater as in claim 1 in which said radiant heater isadapted to heat said first plate to a temperature of between 350*F and450*F.
 13. A copy paper heater as in claim 12 in which said positioningmeans includes a tensioning roller, means mounting said tensioningroller for pivotal movement toward and away from said path, means forbiasing said tensioning roller into said path and a radiant heater forheating said tensioning roller to a temperature of 250*F.